Linear motion variable resistor with bridging contact in slide

ABSTRACT

A slide is movable lengthwise between spaced parallel collector and resistance strips. The slide has a transverse opening through it, in which is disposed bridging contact means that project from opposite sides of the slide. Resilient means press the contact means and both the strips toward one another to hold them in engagement.

United States Patent Inventor Mogens W. Bang Ridgway, Pa.

Appl. No. 65,134

Filed Aug. I9, 1970 Patented Sept. 7, 1971 Assignee Stackpole Carbon Company St. Marys, Pa.

LINEAR MOTION VARIABLE RESISTOR WITH BRIDGING CONTACT IN SLIDE 9 Claims, 10 Drawing Figs.

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[56] References Cited UNITED STATES PATENTS 2,976,507 3 1901 Di Girolamo et al. 338/I80 3,465,277 9/1909 Bang 338 183 3,510,821 5 1970 Eberwein et al. 338 183 3,551,871 12 1970 Eberwein et al. 338 183 x Primary Examiner-Lewis H. Myers Assistant ExaminerD. A. Tone Attorney-Brown, Murray, Flick & Peckham ABSTRACT: A slide is movable lengthwise between spaced parallel collector and resistance strips. The slide has a transverse opening through it, in which is disposed bridging contact means that project from opposite sides of the slide. Resilient means press the contact means and both the strips toward one another to hold them in engagement.

LINEAR MOTION VARIABLE RESISTOR WITH BRIDGING CONTACT IN SLIDE It is among the objects of this invention to provide a linear motion variable resistor, in which spring-pressure is constantly maintained against bridging contact means to maintain the latter in firm contact with a resistance element and a collector and to compensate for wear.

The invention is illustrated in the accompanying drawings, inwhich:

FIG. I is a side view, partly broken away, of a linear motion potentiometer;

FIG. 2 is an enlarged fragmentary longitudinal sectiontaken on the line II-Il of FIG. I;

FIG. 3 is an enlarged cross section taken on the line III-III of FIG. 2; I 7

FIG. 4 is a fragmentary side view of a slide with'its bridging contacts, showing a modification;

FIGS. 5 and 6 are cross sections taken on the lines V-V and VI-VI, respectively, of FIG. 4;

FIG. 7 is a side view, similar to FIG. 4, of a further modification; and

FIGS. 8, 9 and 10 are views similar to FIGS. 4 to 6 of a further embodiment of the invention.

Referring to FIGS. 1 to 3 of the drawings, the long rectangular housing 1' of a variable resistor, such as a potentiometer, is provided along itsfront' or top with a central slot 2'extending lengthwise of the housing for nearly its full length. Slidably mounted in the slot for movement lengthwise of the housing is a rectangular slide 3 that" has laterally opening grooves 4 in its opposite sides receiving the sidewalls of the housing slot to hold and guide the slide. The slide may be moved'in-any suitable manner, such as by a. projection or knob 5.

Inside thehousinga metal collector strip6 and an" electrical resistance strip. 7 are mounted against its opposite sides in parallel relation to each other. The collector strip isprovided with an integral terminal 8- that extends through the back or bottom of thehousing, andeach endof the resistance strip-is connected to another terminal 9 likewise extending through" the back. The slide 3 has a portion extending between these two strips, from which it is spaced. This portion of the slide is an-open frame 10. that is parallel, or nearly so, to the collector and resistance strips. The frame preferably is rectangular.

-Disposed in the opening throughitheframe, but projecting form its opposite sides, is. apair of rollers 1'2 and I3, preferably made of carbon: Carbon as used herein is intended to cover graphite also. The diameter of each roller is considerably lessthan the distance between the two strips, but greater'than half that distance. The rollers are provided with necks 14 that project into openings in opposite sides of the frame. The openings forthe necks of roller 13 are transverse slots 15 that the necks fit rather snugly. The-openings for the othertwo necks are enlargedrecesses 16, in which the necks can move radially in all directions.

It is a feature of this invention that the two rollers are pressed against each other in" such a manner that they press against the collector and resistance element, whereby the rollers forrn bridging contact means between the two strips. Accordingly, a spring carried by the slide-presses roller 12. against the other roller. Since each roller extends more than halfway across the space between thetwo strips 6 and 7, the pressure of the rollers against each" other forces them in opposite directions so that one'projects'from oneside of the slideframe l0 and the other projects from the opposite side, as-shown in FIG. 2. As the slide is moved lengthwise-of the'housing,.the rollers roll upon each other and along the'two'strips.

The-springpreferably includes a body 18 that has end por-' tions clipped around three sides of one side-of the frame and projecting into notches l9 inthe-frame. The spring body holds itself inplace'by spring pressure. At theends of the body thereare laterally projecting leafspring fingers 20 that are reversely bent and press against the side of the necks of roller 12, thereby pushing the roller toward the other roller. As the rollers wear, the spring willcontinue to hold them in engagement with each-other and with the strips.

In the modification shown in FIGS. 4, 5 and 6, the contact rollers 22 and 23 are not offset like those just described, but have their axes in a common plane perpendicular to the resistance strip 24 and the collector strip 25. They are held in this position by their necks 26, which project into slots 27 in opposite sidewalls of the rectangular frame 28 of a slide, by which the rollers are rolled along the strips. To continually press the. strips and rollers together, the collector strip is not mounted against one side of the potentiometer housing as in FIG. 2',.but is spaced from it by a conductor strip 29 engaging the housing 30. These two strips are integrally connected along one edge by resilient means integral therewith. The resilient means is formed from a U-shaped spring area between the adjoining edges of the two strips 25 and 29. It is produced by folding the metal from which the strips are formed,.so that the two strips are substantially parallel and spaced a slight distance apart. In order'to improve the flexibility of this unit, the spring preferably is provided with alarge number of parallel slots 31 separating it into a plurality of spring fingers 32.

The embodiment of the invention shown in FIG. 7 is basically the same asthe one just described. The only difference is inthe way the rollers 35 are held in the slide frame 36. They have flat ends without necks. Their ends are spaced from the adjacent sidewalls of the frame by small bosses 37 projecting from the frame. Lateral movement of the rollers in the frame is prevented by'parallel'ribs 38' integral with the frame beside the side'of therollers.

A further modification of the invention is illustrated in FIGS. 8, 9' and 10' of the drawings, wherein a single carbon block 41 has been'substituted for a pair of rollers. This block is disposed in the rectangular frame 42' of a slide between a resistance strip' 43 and a collector strip 44. The block projects from both. sides of the frame into' engagement with the two strips. The side of the block engaging the resistance strip is taperedto'forma-line contact with the strip as shown in FIG.

' 9". The opposite side of the block preferably is provided with a pair of integral bosses 4'6 spaced lengthwise of the collector strip 44 that they engage. The collector strip is pressed against the bosses by. U-shapedspringfingers47 integrally connecting one edge of that strip with the adjacent edge of a conductor strip'48 engaging a sidewall of the housing. Accordingto the provisions of the patent statutes, I have expl'ainedthe principle ofmy invention and have illustrated and described what I now consider to represent its best embodiment; However, I desire'to have it understood that, within the scope of the appendedclaims,.the invention-may be practiced otherwise than as specifically illustrated and described.

I'claim: 1'. A variable resistor comprising spaced parallel collecto and resistance strips, a slide between said strips movable lengthwise thereof, the slide having a transverse opening therethrough, bridging contact means carried in said opening and projectingfrom opposite sides of the slide, said means being movable bodily insaid opening perpendicularly to said strips, and resilient means pressing said contact means and both of said strips toward one another to hold the contact means in engagement with the strips.

2. A variable resistor acbording to claim 1, in which said resilient means press the' collector strip against said contact means.

3. A variable resistor according to claim I, in which said contact means isa single carbon block, and said resilient means'pressthe collector strip against said block.

4. A variable resistor'according' to" claim I, in which said 'resilient means includes a conductor strip extending lengthwise of the collector strip, and'resilient U-shaped means integrally joined to two adjacent edges of the conductor and collector strips and urging them'apart.

5. A variable resistor'according to claim 1, in which said contact means is a pair-ofparallel rollers disposed side by side in said opening in engagement with each other with their axes extending across the strips, one of the rollers projects from one side of the slide and the other roller projects from the opposite side, and said resilient means press the rollers together as well as against said strips.

6. A variable resistor according to claim 5, in which the rollers are offset relative to each other lengthwise of said strips, and said resilient means is spring means compressed between one of the rollers and the adjacent side of said slide opening.

7. A variable resistor according to claim 6, in which said rollers are provided with necks and the wall of said opening is provided with transverse slots receiving the necks of one roller, and said wall is provided with enlarged recesses receiving the other pair of necks. Said spring means being compressed between said other pair of necks and said adjacent side of the slide opening.

8. A variable resistor according to claim 5, in which the axes of said rollers lie in a plane perpendicular to said strips, and said resilient means press the collector strip against the adjoining roller.

9. A variable resistor according to claim 8, in which said resilient means includes a conductor strip extending lengthwise of the collector strip, and resilient U-shaped means integrally joined to two adjacent edges of the conductor and collector strips and urging them apart. 

1. A variable resistor comprising spaced parallel collector anD resistance strips, a slide between said strips movable lengthwise thereof, the slide having a transverse opening therethrough, bridging contact means carried in said opening and projecting from opposite sides of the slide, said means being movable bodily in said opening perpendicularly to said strips, and resilient means pressing said contact means and both of said strips toward one another to hold the contact means in engagement with the strips.
 2. A variable resistor according to claim 1, in which said resilient means press the collector strip against said contact means.
 3. A variable resistor according to claim 1, in which said contact means is a single carbon block, and said resilient means press the collector strip against said block.
 4. A variable resistor according to claim 1, in which said resilient means includes a conductor strip extending lengthwise of the collector strip, and resilient U-shaped means integrally joined to two adjacent edges of the conductor and collector strips and urging them apart.
 5. A variable resistor according to claim 1, in which said contact means is a pair of parallel rollers disposed side by side in said opening in engagement with each other with their axes extending across the strips, one of the rollers projects from one side of the slide and the other roller projects from the opposite side, and said resilient means press the rollers together as well as against said strips.
 6. A variable resistor according to claim 5, in which the rollers are offset relative to each other lengthwise of said strips, and said resilient means is spring means compressed between one of the rollers and the adjacent side of said slide opening.
 7. A variable resistor according to claim 6, in which said rollers are provided with necks and the wall of said opening is provided with transverse slots receiving the necks of one roller, and said wall is provided with enlarged recesses receiving the other pair of necks. Said spring means being compressed between said other pair of necks and said adjacent side of the slide opening.
 8. A variable resistor according to claim 5, in which the axes of said rollers lie in a plane perpendicular to said strips, and said resilient means press the collector strip against the adjoining roller.
 9. A variable resistor according to claim 8, in which said resilient means includes a conductor strip extending lengthwise of the collector strip, and resilient U-shaped means integrally joined to two adjacent edges of the conductor and collector strips and urging them apart. 